Methods and systems for electroplating wafers

ABSTRACT

Improved methods and systems for electroplating wafers are described herein. The method includes the acts of introducing a wafer which is coupled to an electrode into an electroplating cell having a counter electrode; maintaining a flow of a plating solution through the cell for electroplating the wafer; removing the wafer from the cell; stopping the flow of the plating solution through the cell; maintaining a volume of plating solution within the cell sufficient to keep the counter electrode submerged during stoppage of flow; removing the plating solution within the cell; and repeating the above steps for a subsequent wafer. By stopping the flow of plating solution after completion of plating one or more wafers, a consumption rate of additives enhancing electroplating properties is reduced, a production rate of breakdown products produced during electroplating is reduced, plating solution useable life is increased, and a need for plating solution analysis is reduced.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to methods and systems for electroplating substrates, such as those utilized for damascene electroplating of write coils in magnetic heads.

2. Description of the Related Art

The demand for manufacturing semiconductor integrated circuit (IC) devices, such as computer chips with high circuit speed, high-packing density, and low power dissipation, requires the downward scaling of feature sizes in ultra-large-scale integration (ULSI) and very-large-scale integration (VLSI) structures. The trend to smaller chip sizes and increased circuit density requires the miniaturization of interconnect features which severely penalizes the overall performance of the structure because of increasing interconnect resistance and reliability concerns such as fabrication of the interconnects and electromigration. Magnetic heads with inductive write coils also feature miniaturization requirements to increase areal storage densities on magnetic disks and reduction of coil resistance.

Historically, such structures have utilized aluminum and aluminum alloys as the metallization on silicon wafers, with silicon dioxide being the dielectric material. In general, openings were formed in the silicon dioxide dielectric layer in the shape of vias and trenches which were then metallized to form the interconnects. Increased miniaturization, however, has required these openings to be at submicron sizes (e.g., 0.5μ and lower). To achieve such miniaturization, industries have moved to the use of copper instead of aluminum as the metal to form the connection lines and interconnects in the chip. Copper has a lower resistivity than aluminum and the thickness of a copper line for the same resistance can be thinner than that of an aluminum line. Copper-based interconnects therefore represent the most foreseeable future trend in the fabrication of such devices. Copper can be deposited on substrates by plating (such as electroless and electrolytic), sputtering, plasma vapor deposition (PVD), and chemical vapor deposition (CVD). It is generally recognized that a plating-based deposition is the best method to apply copper to the device since it can provide high deposition rates and low system costs.

Referring to FIG. 1, a plating system 100 of the prior art is shown. Plating system 100 is used for electroplating copper onto a wafer 112 which is coupled to a cathode. Plating system 100 may be of the type provided by Semitool, Inc. of Kalispell, Mont., U.S.A., for example, the EQUINOX® system platform (EQUINOX is a registered trademark of Semitool, Inc.). System 100 includes an electroplating cell 110 which holds a plating solution 127. Cell 110 is made of a suitable material, such as plastic or other material inert to plating solution 127. Cell 110 is preferably cylindrical in shape, but alternatively may be square or rectangular in shape. Wafer 112 is horizontally disposed at the upper part of cell 110 and may be any type substrate, such as a silicon, ceramic or other material having openings including trenches and vias to be plated. A wafer surface 112 a of wafer 112 is typically coated with a seed layer of copper or other metal to initiate plating thereon. A copper seed layer may be applied by sputtering, plasma vapor deposition (PVD), chemical vapor deposition (CVD), or the like. An anode 113 is preferably circular for wafer plating and is horizontally disposed at the lower part of cell 110, forming a space therein between wafer 112 and anode 113. Anode 113 is a soluble electrode which is consumed during processing. Suitable soluble anodes include copper and other copper alloys such as copper phosphate. The anode and cathode are electrically connected by wiring 114 and 115, respectively, to a power supply 116. In electroplating system 100, wafer 112 has a negative charge so that copper ions in the solution are reduced to form plated copper metal on wafer surface 112 a. An oxidation reaction takes place at anode 113 causing copper metal to go into solution.

Plating system 100 further includes a plating solution holding tank 119 from which a plating solution 127 is drawn via a pump 122 through a plating solution inlet transport line 117, a flow measurement device 151, and an inlet valve 140 to an inlet 110 a of cell 110. Plating solution 127 flows through cell 110 and thereby contacts wafer 112 and anode 113, filling the space therein between them with the solution. A rotor 130 holds wafer 112 in position and a rotor 131 holds anode 113 in place. Rotors 130 and 131 alternatively may be a flange, plate, or other similar device. Plating solution 127 exits cell 110 through an overflow weir 125 into outlet 110 b and is recycled into tank 119 through a plating solution transport line 118. During operation of plating system 100 to plate wafer 112, plating solution 127 continuously flows through the system at a predetermined plating flow rate. The plating flow rate may be, for example, between 2 to 6 gallons per minute (g/m). This forms a substantially uniform electrolyte composition in the system and contributes to the overall effectiveness of the wafer plating. Flow of plating solution 127 through plating system 100 is controlled by a flow control mechanism which includes pump 122 and inlet valve 140. Additionally, the flow control mechanism includes a flow measurement device 151, such as a flow meter, and a closed feedback loop 150 for more precise control over the flow of plating solution 127.

During operation of plating system 100, copper metal is plated on wafer surface 112 a when power supply 116 is energized. A pulse current, direct current (DC), reverse periodic current, or other suitable current may be employed. The electroplating process results in depletion of the copper concentration of plating solution 127. Copper deposits must be uniform and capable of filling the extremely small trenches and vias of the device. These important properties are typically achieved using multi-component plating solutions, which include organic and inorganic components. Typical plating solution 127 formulations use highly stable electrolytes containing copper sulfate and sulfuric acid. As an example, copper concentration in these electrolytes may be between 12-60 grams/liter (g/l) and sulfuric acid 1-240 g/l.

Other components added to the plating solution are present in relatively small amounts. These components are organic additives and chloride ions. The organic additives, depending on the concentration and chemical composition, affect the properties of the electrodeposited copper including uniformity, hardness, ductility, tensile strength, grain size, etc. These additives for enhancing electroplating properties, which react at the wafer surface during electroplating, fall into three major categories. Accelerators are compounds that contain pendant sulfur atoms that locally accelerate deposition where they are adsorbed. Suppressors are polymers, such as polyethylene glycols, which have the ability to form a current-suppressing film on the entire wafer surface. The third category of organic additives are levelers, which are secondary suppressors and work only on the protruding surfaces where mass transfer is most effective.

After completing the electroplating of one or more wafers, the flow through pump 122 is set and maintained at a reduced “idle flow” rate. This reduced idle flow rate may be, for example, between 1 to 1.5 g/m. During this time period, no wafers are being electroplated. At some point in time, however, subsequent wafers will be electroplated where pump 122 is once again set and maintained at the higher plating flow rate.

In addition to reacting at the surface of the wafer during electroplating, the additives of the plating solution undesirably react at the surface of anode 113 within cell 110 during electroplating and idle flow during non-plating periods. Further, there are other interactions between the additives and inorganic compounds which cause decomposition and modification of initial organic compounds. These breakdown products ideally need to be kept below a threshold level in order to provide the most uniform of copper deposition and highest capability of filling the extremely small trenches and vias of the device. Thus, monitoring these breakdown products must be performed at least once every four to six hours by analyzing the composition of the bath during idle flow. Also, replacement of up to 20% may be done daily to maintain the plating solution in steady state. Both of these requirements result in a large amount of time and labor for plating solution analysis and control. This is especially true when system utilization is less than 100%.

Accordingly, what are needed are improved methods for electroplating wafers as well as improved systems for performing such methods.

SUMMARY

Improved methods and systems for electroplating wafers are described herein. The method includes the acts of introducing a wafer which is coupled to an electrode (e.g. a cathode) into an electroplating cell having a counter electrode (e.g. an anode); maintaining a flow of a plating solution through the cell for electroplating the wafer; removing the wafer from the cell; stopping the flow of the plating solution through the cell; maintaining a volume of plating solution within the cell sufficient to keep the counter electrode submerged during stoppage of flow; removing the plating solution within the cell; and repeating the above steps for a subsequent wafer.

By stopping the flow of plating solution after completion of plating one or more wafers, a consumption rate of additives enhancing electroplating properties is reduced, a production rate of breakdown products produced during electroplating is reduced, plating solution useable life is increased, and a need for plating solution analysis is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the present invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings:

FIG. 1 is a system for electroplating wafers of the prior art;

FIG. 2 is a flowchart which describes an improved method for electroplating wafers in accordance with the present invention;

FIG. 3 is a system for electroplating wafers in accordance with the present invention; and

FIG. 4 is a system for electroplating wafers according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In describing the preferred embodiment of the present invention, reference will be made herein to FIGS. 1-4 of the drawings in which like numerals refer to like features of the invention. Features of the invention are not necessarily shown to scale in the drawings.

FIG. 2 is a flowchart which describes an improved method for electroplating wafers in accordance with the present invention. FIGS. 3-4 are process flow diagrams of plating systems 300 and 400 of the present invention within which the steps in the flowchart of FIG. 2 may be employed. While the systems and methods are described primarily with reference to plating a silicon wafer, it will be appreciated by those skilled in the art that other substrates may be plated. Although any suitable system platform may be utilized, the plating system may be based on the type provided by Semitool, Inc. of Kalispell, Mont., U.S.A., for example, the EQUINOX® system platform (EQUINOX is a registered trademark of Semitool, Inc.).

Referring first to FIG. 3, plating system 300 includes an electroplating cell 110 which holds a plating solution 127. Cell 110 may be made of a suitable material, such as plastic or other material inert to plating solution 127, which forms a reservoir for holding the solution. Cell 110 is preferably cylindrical, but may alternatively be different shapes, such as square or rectangular. A wafer 112, which is coupled to an electrode (e.g. a cathode), is inverted and horizontally disposed at the upper part of electroplating cell 110 and may be any type of substrate, such as a silicon wafer having openings including trenches and vias to be plated. Wafer 112 may be introduced within and removed from cell 110 via a positioning mechanism (e.g. rotor 131). A wafer surface 112 a of wafer 112 is typically coated with a seed layer of copper or other metal to initiate plating thereon. A copper seed layer may be applied by sputtering, plasma vapor deposition (PVD), chemical vapor deposition (CVD) and the like. A counter electrode 113 (e.g. an anode) is preferably circular, but may alternatively be different shapes such as square or rectangular, for wafer plating and is horizontally disposed at the lower part of cell 110, forming a space therein between wafer 112 and counter electrode 113. Counter electrode 113 is a soluble electrode which is consumed during processing. Suitable soluble anodes include copper and other copper alloys such as copper phosphate. Wafer 112 and counter electrode 113 are electrically connected by wiring 114 and 115, respectively, to a power supply 116. In plating system 300, wafer 112 has a negative charge so that copper ions in the solution are reduced thereby forming plated copper metal on wafer surface 12 a. An oxidation reaction takes place at counter electrode 113 causing copper metal to go into solution. Wafer 112 and counter electrode 113 are shown horizontally disposed but may alternatively be vertically disposed in cell 110. Furthermore, wafer 112 and counter electrode 113 may alternatively be disposed in opposite positions.

Plating system 300 further includes a plating solution holding tank 119 from which a plating solution 127 is drawn via a pump 122 through a plating solution inlet transport line 117 and a plating solution inlet valve 140 into an inlet 110 a of cell 110. Plating solution 127 flows through cell 110 and thereby contacts wafer 112 and counter electrode 113, filling the space between them with the solution. Rotor 130 holds wafer 112 in position and rotor 131 holds counter electrode 113 in place. Rotors 130 and 131 alternatively may be a flange, plate, or other similar device. Plating solution 127 exits cell 110 through overflow weir 125 into outlet 110 b, flows through an adjacent plating solution outlet valve 341, and is recycled into tank 119 through plating solution transport line 118. During operation of plating system 100, plating solution 127 continuously flows through the system at a predetermined plating flow rate. The plating flow rate may be, for example, between 2 to 6 gallons per minute (g/m). Such flow forms a substantially uniform electrolyte composition in the system and contributes to the overall effectiveness of the wafer plating. Flow of plating solution 127 through plating system 300 is controlled by a flow control mechanism which includes pump 122, inlet valve 140, and outlet valve 341. Additionally, the flow control mechanism includes a flow measurement device 151, such as a flow meter, and a closed feedback loop 150 for more precise control over the flow of plating solution 127. Note that plating system 300 is similar to plating system 100 of FIG. 1 except that outlet valve 341 has been added to plating solution transport line 118 positioned adjacent outlet 110 b of cell 110.

The composition of plating solution 127 may vary widely depending on the substrate to be electroplated and the type of copper deposition desired. Exemplary plating solutions include copper fluoborate, copper pyrophosphate, copper cyanide, copper phosphonate, and other copper metal chelates such as methane sulfonic acid. One preferred plating solution is copper sulfate in an acid solution. The concentration of copper and acid may vary over wide limits. For copper or copper ions, compositions generally vary up to 25 grams/liter (g/l) or more preferably 15 to 20 g/l. The acidic composition is typically sulfuric acid in an amount up to about 300 g/l or more, preferably 150 to 200 g/l. Chloride ions may be used in the plating solution at levels up to about 90 mg/l. Other components added to the plating solution are present in relatively small amounts. These components are organic additives and chloride ions. The additives for enhancing electroplating properties, depending on the concentration and chemical composition, affect the properties of the electrodeposited copper including uniformity, hardness, ductility, tensile strength, etc. A particularly desirable additive composition uses a mixture of aromatic or aliphatic quaternary amines, polysulfide compounds, polyimines and polyethers. Other additives include metaloids such as selenium, tellurium and sulfur compounds.

A method of electroplating wafer 112 of FIG. 2 which may utilize system 300 of FIG. 3 is now described. Beginning at a starting point 202 in FIG. 2, wafer 112 is introduced into electroplating cell 110 having counter electrode 113 with use of the positioning mechanism (step 204 of FIG. 2). During operation of system 300, a flow of plating solution 127 is maintained through cell 110 at a predetermined plating flow rate (step 206 of FIG. 2). The flow is controlled by the flow control mechanism which may include pump 122, inlet valve 140 and outlet valve 341; pump 122 is engaged and valves 140 and 341 are opened. Additionally, the flow control mechanism includes a flow measurement device 151, such as a flow meter, and a closed feedback loop 150 for more precise control over the flow of plating solution 127. Over some period of time, wafer 112 is electroplated within cell 110. Upon completion of electroplating wafer 112, the wafer is removed from cell 110 with use of the positioning mechanism (step 208 of FIG. 2). Additional wafers of the same set or batch may thereafter be plated by repeating these steps (step 210 of FIG. 2). Preferably, the wafer includes a plurality of magnetic head structures for which damascene copper electroplating is needed. Typically, the time period between electroplating wafers of the same set is relatively short. The time period may be, for example, between 0 and 60 minutes.

Once the electroplating of the wafer(s) is completed as identified at step 210, flow of the solution through cell 110 is stopped by turning off or disengaging pump 122 as well as closing inlet valve 140 and outlet valve 341 (step 212 of FIG. 2). During stoppage of flow, the volume of plating solution 127 is maintained within cell 110 (step 214 of FIG. 2). This volume is sufficient to keep counter electrode 113 submerged between electroplating runs. An indefinite time period lapses until the next wafer or wafer set is electroplated (step 216 of FIG. 2). This time period may typically be, for example, between 1 and 24 hours.

For the next set of wafers to be electroplated, the volume of the plating solution maintained within cell 110 is removed just prior to electroplating the next wafer (step 218 of FIG. 2). To do this, the plating solution may be recycled into solution holding tank 119 by opening inlet valve 140 and outlet valve 341. The flow of plating solution 127 is then started again by initializing and operating pump 122 at the plating flow rate (step 220 of FIG. 2).

As indicated, the above method is applicable when electroplating different sets or batches of wafers. For a first set of wafers, steps 204, 206, 208 and 210 of FIG. 2 are repeated. Upon completion of the first set, steps 212, 214 and 216 of FIG. 2 are performed until a next set of wafers is to be plated. Steps 218 and 220 of FIG. 2 are then performed to initiate the electroplating of the next set of wafers by again repeating steps 204-210.

During operation of plating system 300 (e.g. step 206 of FIG. 2), copper metal is plated on wafer surface 112 a when power supply 116 is energized. A pulse current, direct current (DC), reverse periodic current or other suitable current may be employed. The electroplating process results in depletion of a copper concentration of plating solution 127. Note that the additives for enhancing electroplating properties typically undesirably react at the surface of counter electrode 113 within the cell during electroplating as well as during idle flow of the plating solution during non-production periods. Further, there are other interactions between the additives and inorganic compounds which cause decomposition and modification of initial organic compounds. These breakdown products ideally need to be kept below a threshold level in order to provide the most uniform of copper deposition and highest capability of filling the extremely small trenches and vias of the device. As such, analysis of these breakdown products is performed at least once every four to six hours by analyzing the composition of the plating solution during idle flow under methods and systems of the prior art. Also, replacement of up to 20% may be done daily to maintain the plating solution in steady state during operation of plating systems of the prior art.

In accordance with the present techniques, the flow of plating solution 127 is stopped but a volume of plating solution 127 is maintained within cell 110 sufficient to keep counter electrode 113 submerged between electroplating runs (see steps 212 and 214 of FIG. 2). These steps preserve an organic film which grows on counter electrode 113. Further, this stoppage of flow reduces a consumption rate of the additives; reduces a production rate of breakdown products produced during electroplating; increases plating solution useable life; and reduces a need for analysis of the plating solution from once every four to six hours to once every eight hours. Upon identifying the need to electroplate subsequent wafers, the volume of plating solution 127 within the cell is removed (e.g. recycled into the plating solution holding tank) by opening outlet valve 341.

Removing the plating solution from the system is performed and new plating solution is added to the system either simultaneously or after the recycling in substantially the same amount. The new solution is preferably a single liquid containing all the materials needed to maintain the electroplating system. The addition/removal mechanism maintains the plating solution in steady-state during operation of the plating system.

Referring now to FIG. 4, plating system 400 is similar to plating system 300 of FIG. 3 except that a plating solution drain transport line 420 positioned adjacent an outlet 110 c of cell 110, a plating solution drain valve 442, and a plating solution drain tank 421 have also been provided. All previous descriptions relating to the method of FIG. 3 hold true with the following difference. In preparation for subsequent wafers after the maintenance of the volume within the cell (step 214 of FIG. 2), plating solution in cell 110 is removed through plating solution drain transport line 420 into plating solution drain tank 421 by opening drain valve 442. This step corresponds to step 218 of FIG. 2. Flow of the plating solution through plating system 400 is thereafter controlled by the flow control mechanism which includes pump 122, inlet valve 140, outlet valve 341, and drain valve 442. In particular, after the plating solution is removed to drain tank 421, drain valve 442 is closed, valves 140 and 341 are opened, and pump 122 is activated to facilitate the plating flow rate.

Note that the techniques for engaging/disengaging the pump, opening/closing of the valves, and identifying various conditions for change (e.g. wafer electroplating completed, new wafer set introduced, etc.), may be implemented in whole or in part manually by an end user(s) of the system or by computer control. If done by computer control, software instructions may be written in accordance with the described logic, stored in memory, and executed by a computer processor for performing the method.

Thus, a method of electroplating wafers of the present invention includes the steps of: for a first set of wafers: (a) introducing a wafer coupled to an electrode into an electroplating cell having a counter electrode; (b) maintaining a flow of a plating solution through the cell for electroplating the wafer; (c) removing the wafer from the cell; and (d) repeating steps a to c for electroplating additional wafers of the first set. The method continues with the steps of (e) stopping the flow of the plating solution through the cell after electroplating the first set of wafers; and (f) maintaining a volume of plating solution within the cell sufficient to keep the counter electrode submerged during stoppage of flow. For a subsequent set of wafers, the method continues with the steps of (g) removing the plating solution within the cell; and (h) reperforming steps a to d for electroplating the subsequent set of wafers.

A system of the present invention includes an electroplating cell for electroplating a wafer; a positioning mechanism to introduce and remove the wafer from the cell; and a flow control mechanism to maintain a flow of plating solution through the cell for electroplating the wafer and to stop the flow thereafter. The flow control mechanism also maintains a volume of plating solution within the cell sufficient to keep an electrode of the cell submerged during stoppage of flow, and removes the volume of plating solution from the cell prior to electroplating a subsequent wafer. The removal of plating solution may be done by draining the cell for recycling within a holding tank or for disposal via a drain/waste tank.

It is to be understood that the above is merely a description of preferred embodiments of the invention and that various changes, alterations, and variations may be made without departing from the true spirit and scope of the invention as set for in the appended claims. Few if any of the terms or phrases in the specification and claims have been given any special meaning different from their plain language meaning, and therefore the specification is not to be used to define terms in an unduly narrow sense. 

1. A method of electroplating wafers, comprising: a. introducing a wafer coupled to an electrode into an electroplating cell having a counter electrode; b. maintaining a flow of a plating solution through the cell for electroplating the wafer; c. removing the wafer from the cell; d. stopping the flow of the plating solution through the cell; e. maintaining a volume of plating solution within the cell sufficient to keep the counter electrode submerged during stoppage of flow; f. removing the plating solution within the cell; and g. repeating steps a to c for electroplating a subsequent wafer.
 2. The method of claim 1, wherein the act of maintaining the flow comprises engaging a pump for a predetermined plating flow rate.
 3. The method of claim 1, wherein the act of stopping the flow comprises the further act of disengaging a pump.
 4. The method of claim 1, wherein the act of stopping the flow comprises closing a valve.
 5. The method of claim 1, wherein the act of removing the plating solution comprises releasing the plating solution into a tank.
 6. The method of claim 1, wherein the counter electrode comprises one of titanium coated with one of platinum, platinized titanium, platinized niobium, iridium oxide and ruthenium oxide.
 7. The method of claim 1, wherein the plating solution is an electrolytic solution comprising copper ions and additives for enhancing electroplating properties.
 8. The method of claim 1, wherein the plating solution is an electrolytic solution comprising copper ions and additives for enhancing electroplating properties, and wherein the additives comprise at least one of aromatic quaternary amines, aliphatic quaternary amines, polysulfide compounds, polyimines, polyethers, selenium, tellurium and sulfur compounds.
 9. The method of claim 1, further comprising: wherein the plating solution is an electrolytic solution comprising copper ions and additives for enhancing electroplating properties; wherein stoppage of flow reduces a consumption rate of the additives; wherein stoppage of flow reduces a production rate of breakdown products produced during electroplating; wherein stoppage of flow increases plating solution useable life; and wherein stoppage of flow reduces a need for analysis of the plating solution.
 10. A method of electroplating wafers, comprising: for a first set of wafers to be electroplated: a. introducing a wafer coupled to an electrode into an electroplating cell having a counter electrode; b. maintaining a flow of a plating solution through the cell for electroplating the wafer; c. removing the wafer from the cell; d. repeating steps a to c for electroplating additional wafers of the first set; e. stopping the flow of the plating solution through the cell after electroplating the first set of wafers; f. maintaining a volume of plating solution within the cell sufficient to keep the counter electrode submerged during stoppage of flow; for a subsequent set of wafers: g. removing the plating solution within the cell; and h. performing steps a to d for electroplating the subsequent set of wafers.
 11. The method of claim 10, wherein the act of maintaining the flow comprises activating a pump.
 12. The method of claim 10, wherein the act of stopping the flow comprises the further act of deactivating a pump.
 13. The method of claim 10, wherein the act of stopping the flow comprises closing a valve.
 14. The method of claim 10, wherein the act of removing the plating solution comprises releasing the plating solution into a holding tank.
 15. The method of claim 10, wherein the counter electrode comprises one of titanium coated with one of platinum, platinized titanium, platinized niobium, iridium oxide and ruthenium oxide.
 16. The method of claim 10, wherein the plating solution is an electrolytic solution comprising copper ions and additives for enhancing electroplating properties.
 17. The method of claim 10, wherein the plating solution is an electrolytic solution comprising copper ions and additives for enhancing electroplating properties, and wherein the additives comprise at lease one of aromatic quaternary amines, aliphatic quaternary amines, polysulfide compounds, polyimines, polyethers, selenium, tellurium and sulfur compounds.
 18. The method of claim 10, further comprising: wherein the plating solution is an electrolytic solution comprising copper ions and additives for enhancing electroplating properties; wherein stoppage of flow reduces a consumption rate of the additives; wherein stoppage of flow reduces a production rate of breakdown products produced during electroplating; wherein stoppage of flow increases plating solution useable life; and wherein stoppage of flow reduces a need for analysis of the plating solution.
 19. A system comprising: an electroplating cell for electroplating a wafer; a positioning mechanism to introduce and remove the wafer from the cell; a flow control mechanism to maintain a flow of plating solution through the cell for electroplating the wafer and to stop the flow thereafter; the flow control mechanism to further maintain a volume of plating solution within the cell sufficient to keep an electrode of the cell submerged during stoppage of flow; and the flow control mechanism to further remove the volume of plating solution from the cell prior to electroplating a subsequent wafer.
 20. The system of claim 19, wherein the positioning mechanism comprises a rotor.
 21. The system of claim 19 wherein the flow control mechanism comprises a pump.
 22. The system of claim 19, wherein the flow control mechanism comprises a plating solution inlet valve to maintain and stop the flow.
 23. The system of claim 19 wherein the flow control mechanism comprises a plating solution outlet valve to maintain and stop the flow.
 24. The system of claim 19, wherein the flow control mechanism comprises a plating solution drain valve.
 25. The system of claim 19, wherein the flow control mechanism comprises: a pump; a plating solution inlet valve; and a plating solution outlet valve.
 26. The system of claim 19, wherein the flow control mechanism comprises: a pump; a plating solution inlet valve; a plating solution outlet valve; and a plating solution drain valve.
 27. The system of claim 19, further comprising: a power supply having an anode and a cathode for coupling to the wafer, the anode comprising the electrode of the cell; a plating solution holding tank from which the plating solution is drawn; a plating solution inlet transport line connected to the holding tank which facilitates flow of the plating solution from the holding tank to the cell through an inlet valve of the flow control mechanism; a pump of the flow control mechanism connected to the inlet transport line; and a plating solution outlet transport line connected to the cell which facilitates flow of the plating solution from the cell to the holding tank through an outlet valve of the flow control mechanism.
 28. The system of claim 19, further comprising: a power supply having an anode and a cathode for coupling to the wafer, the anode comprising the electrode of the cell; a plating solution holding tank from which the plating solution is drawn; a plating solution inlet transport line connected to the holding tank which facilitates flow of the plating solution from the holding tank to the cell through an inlet valve of the flow control mechanism; a pump of the flow control mechanism connected to the inlet transport line; a plating solution outlet transport line connected to the cell which facilitates flow of the plating solution from the cell to the holding tank through an outlet valve of the flow control mechanism; and a plating solution drain transport line connected to the cell which facilitates removal of the volume of plating solution within the cell sufficient to keep the electrode of the cell submerged during stoppage of flow to a plating solution drain tank through a drain valve to remove the volume of plating solution from the cell. 